Telepresence systems allow a user at one location to view a remote location (e.g., a conference room) as if they were present at the remote location. Mutually-immersive telepresence system environments allow the user to interact with individuals present at the remote location. In a mutually-immersive environment, the user is provided a display apparatus including a projection surface that typically surrounds the user. Cameras are positioned about the display area to collect images of the user. Live color images of the user are acquired by the cameras and subsequently transmitted to the remote location, concurrent with projection of live video from the remote location on the projection surfaces surrounding the user. The user is able to move about within the display area; thus algorithms are needed to track the movements of the user, particularly movements of the user's head.
Conventional head tracking methods include generating a representation of a user's head based on the detection of the user's eyes or other facial features. An example of such a method would be to use the retro-reflectivity property of the human eye, when illuminated by light, to detect and track head position. A drawback associated with such an approach is that the head of the person being tracked must always be facing a camera. If the user turns away from the camera, eye reflectivity can no longer be detected. Thus, head position tracking cannot be accurately maintained.
Another conventional head tracking method calls for the local user to wear tracking hardware, such as is used for motion capture in computer graphics, and to transform the position information obtained from the tracking hardware into a bounding box image based on the lens focal length of the tracking hardware and the particular system geometry. A drawback associated with this approach is that the local user would have to be burdened with wearing the oftentimes cumbersome tracking hardware. Also, the tracking hardware degrades final image quality, as the tracking hardware would be visible in any resulting image.
What is needed is an improved technique for tracking the movement and positioning of an object, for example, a person's head. What is further needed is a technique for determining the angular orientation of such an object. It is toward these ends that the present invention is directed.